Studies in sheep demonstrated that close contacts seen under light microscopy were actual synaptic contacts by electron microscopy.6 Future studies should clarify whether dynorphin neurons contain progesterone receptors in humans as seen in other species including sheep.5 The distribution of dynorphin fibers in this study was PF-543 Citrate consistent with a previously reported distribution of dynorphin in the human.12 Studies have demonstrated that GnRH neurons have close contacts with other endogenous opioid peptides in humans. The GnRH neurons with intact cell bodies and dendrites were identified in the 3 female subjects. These cells were equally distributed in the preoptic area, anterior hypothalamus, and mediobasal hypothalamus. The GnRH neurons displayed common fusiform morphology (Physique 1A-C) and size of both cell bodies (12.5 0.3 m mean width, 26.8 0.7 m mean length) and dendrites (82.9 7.5 m mean length, range 10 to 330 m). Dynorphin fibers were identified in the preoptic area, anterior, and mediobasal hypothalamus and exhibited close contacts with GnRH cell bodies and dendrites (Physique 1A-C). Dynorphin close contacts were identified on 87.5% of the GnRH cells analyzed (Table 2). GnRH neurons received an average of 2.3 1.8 contacts/cell (Table 2). The percentage of GnRH neurons that had close contacts with dynorphin and the average number of close contacts for each subject is listed in Table 2. The majority, 62.5%, of GnRH neurons were observed to possess 1 close contacts with dynorphin TPO fibers (Determine 2). The distribution of these close contacts did not differ among neuroanatomical regions including the preoptic area, anterior hypothalamus, or mediobasal hypothalamus, or in the number of close contacts (data not shown). The mean number of close contacts identified around the GnRH dendrites (1.69 1.53) was greater than the cell bodies (0.59 1.08; .001) but this difference was not significant when corrected for length (0.028 0.03 contacts/m, 0.023 0.04 contacts/m respectively; = .15). Examples of dynorphin fibers and preabsorbed immunocytochemical control for dynorphin staining with elimination of specific staining in the preoptic area (POA) are exhibited in Physique 3A and ?andB,B, respectively. The preabsorbed controls for GnRH cell bodies and the elimination controls for both dynorphin and GnRH exhibited no specific staining (data not shown). Open in a separate window Physique 1 Immunocytochemical identification of gonadotropin-releasing hormone (GnRH) neurons (brown). Dynorphin fibers appear as black-beaded varicosities. Dynorphin fibers are observed in close contacts with GnRH neuron dendrite (A) and cell bodies (B-C; black arrows). A and B were acquired at 20 magnification. C was acquired at 40 magnification. Table 2. Summary of GnRH Neurons With Close Contacts From Dynorphin Fibers for Each of the 3 Female Subjects thead th rowspan=”1″ colspan=”1″ Subject /th th rowspan=”1″ colspan=”1″ Percent of GnRH Cells With Dynorphin Close Contacts /th th rowspan=”1″ colspan=”1″ Mean Number of Contacts Per Cell SD /th /thead T-13385.2%2.0 1.5T-18084.2%2.7 2.1T-11194.4%2.2 1.9Total87.5%2.3 1.8 Open in a separate window Abbreviations: GnRH, gonadotropin-releasing hormone; SD, standard deviation. Open in a separate window Physique 2 Percentages of gonadotropin-releasing hormone (GnRH) cells with none, one, or multiple close contacts with dynorphin immunoreactive fibers. Most of the GnRH neurons 40/64 (62.5%) examined received multiple close contacts from dynorphin immunoreactive fibers. Open in a separate window Physique 3 Example of immunocytochemical control for dynorphin staining in the human preoptic area (POA; A). Adjacent control section of the POA incubated with preabsorbed dynorphin antibody (B). Images acquired at 20 magnification. Discussion This study in humans revealed that PF-543 Citrate dynorphin immunoreactive fibers have close contacts with GnRH neurons in the female hypothalamus. This neuroanatomical evidence supports the hypothesis that dynorphin is usually involved in the regulation of GnRH neurons in humans as seen in other species. The morphology and distribution of GnRH cell bodies and fibers we observed in this study was consistent with other reports of GnRH neuron distribution in humans.11 There were a greater number of dynorphin close contacts identified around the dendrite portion of the GnRH neurons compared to the PF-543 Citrate cell bodies. However, the mean dendrite length identified in this study was notably longer than the mean cell body length. When corrected for unit length, there was no difference between the cell bodies and dendrites in the number of close contacts identified from dynorphin fibers. The majority of GnRH neurons identified in this study received PF-543 Citrate multiple contacts from dynorphin fibers. Studies in sheep exhibited that close contacts seen under light microscopy were actual synaptic contacts by electron microscopy.6 Future studies should clarify whether dynorphin neurons contain progesterone receptors in.